This item is a must have for cleaning your 308 AR. The Link separates the upper and lower assemblies, but holds them securely to allow easy breech access for bore cleaning using a Sinclair Rod Guide. Made of Delrin and stainless steel, it is virtually impervious to solvents. The Cleaning Link uses the rear locking pin and rear locking pin hole and installs in seconds. Mfg: Sinclair International SPECS: Will require fitting for most takedown pins other than the Armalite AR-10. Will not work on POF .308 rifles, Windham Weaponry SRC 308, or Colt LE901 with .250 diameter takedown pins, use the AR-15 model 749-002-497.